Technical Abstract:
Justification:
Pectin is a branched polysaccharide that has been used for thickening, coating, and encapsulating. However, few studies have been reported on use of pectin as a base packaging material and as a carrier of nisin for antimicrobial food packaging.
Objective:
The objective of this study was to develop pectin films containing nisin and investigate the antimicrobial functionality of these films in foods.
Methods:
Two types of pectin films were developed in this study: 1. Extruded composite films from pectin and poly(lactic acid) (PP film); 2. Cast composite edible films from pectin and soy protein (PSP film). Nisin was loaded into films either by a diffusion method post extrusion (PP+N film) or by adding to the pectin-soy protein mixture prior to casting (PSP+N film). Each film contained a maximum of 0.5% nisin. Inhibition of Lactobacillus platarum and Listeria monocytogenes by the films were evaluated in MRS, BHI, liquid egg white and orange juice. The mechanical properties of PP films were also determined.
Results:
Both PSP+N film and PP+N film significantly inhibited the growth of L.planturam in MRS and L.monocytogens in BHI. There was no growth of L.planturam or L.monocytogens detected (<10 cfu/ml) in PP+N or PSP+N films while the control had 9 log of L.planturam at 24 h or 9.5 log of LM at 96 h, respectively. L.monocytogens in liquid egg white with PP+N film was reduced from 6.8 log to 2 log while control maintained at 6.5 log after 32 h. Six log reduction of L.monocytogens in orange juice with PP+N film was observed. The incorporation of nisin didn’t affect the tensile strength, flexibility and toughness of PP+N films.
Significance:
This study demonstrated that the pectin films with nisin effectively inactivated L.planturam and L.monocytogens. The use of biobased and biodegradable materials, such as pectin, in combination with nisin has a great potential in antimicrobial food packaging.